Where do you locate your convertors? do you put them in the Window.Resources section? or in the UserControl they are being used for? Neither of these options is good. You should put it in the App.Xaml file and here is why:

Lets look at the following example:

Here is our Window:

1:<Windowx:Class="ConvertorLocation.Window1"

2:xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

3:xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

4:xmlns:my="clr-namespace:ConvertorLocation"

5:Title="Window1"Height="300"Width="300">

6:<Grid>

7:<ItemsControlItemsSource="{Binding}">

8:<ItemsControl.ItemTemplate>

9:<DataTemplate>

10:<my:UserControl1></my:UserControl1>

11:</DataTemplate>

12:</ItemsControl.ItemTemplate>

13:</ItemsControl>

14:</Grid>

15:</Window>

In the Window Code Behind we create a list filled with some DateTime objects:

1:publicpartialclass Window1 : Window

2: {

3:public Window1()

4: {

5: InitializeComponent();

6: List<DateTime> d = new List<DateTime>();

7: d.Add(new DateTime(2005, 10, 2, 15, 22, 28));

8: d.Add(new DateTime(2002, 11, 5, 4, 55, 14));

9: d.Add(new DateTime(2006, 12, 3, 1, 55, 23));

10: d.Add(new DateTime(2004, 2, 1, 5, 26, 1));

11: d.Add(new DateTime(2001, 4, 6, 12, 35, 33));

12: d.Add(new DateTime(2004, 7, 3, 15, 28, 5));

13:this.DataContext = d;

14: }

15: }

16: }

As you can see The template holds a UserControl, here is the UserControl Code: